In the fuelling of gas powered vehicles with compressed fuel gas, typically natural gas or hydrogen, a filling hose is connected to the on-vehicle gas reservoir. To cause the vehicle to receive and store fuel gas under high pressure, the filling hose and connector lines between the pressurized gas source, typically a compressor or reservoir, and vehicle inlet must contain gas under high pressure. When the vehicle tank is full, this high pressure line must be disconnected from the vehicle.
Such lines normally terminate in vehicle connectors. On the vehicle, a one-way valve prevents back-flow of gas from the vehicle into the connecting line, once this disconnection occurs. This one-way valve only closes when the pressure in the connecting line falls below the pressure in the vehicle tank. It is typically difficult to effect a disconnection while the connecting lines are filled with highly pressurized gas. A release of pressure is, therefore, necessary to permit disconnection.
The gas in the connecting line could be vented to the atmosphere. However, for environmental reasons, it is not desirable to vent fuel gas to the atmosphere. To release the pressure in the connecting lines, it is known to divert the high pressure gas to a secure storage reservoir, lowering the pressure of gas within the connecting lines. This "blow-down" operation thereby facilitates disconnecting the lines from the vehicle.
During the blow-down procedure, the vehicle one-way valve is supposed to prevent the reverse flow of gas from the vehicle tank back into the connecting lines. If this one-way valve fails to close completely, any attempt to depressurize the connecting line will be resisted or thwarted. Further, when the valve to the blow-down tank is opened, the tank in the vehicle will feed gas back into the connecting line and the low pressure receiving reservoir or blow-down tank will become flooded with high pressure gas. This renders it inoperative as a low pressure reservoir.
This invention relates to a system for diverting high pressure gas in a line to a lower pressure storage reservoir,--a "blow-down" operation--only under controlled conditions. In particular, the invention addresses the malfunction of one-way valves that will cause excess gas to enter the lines that are being depressurized.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.